1. Field of the Invention
The invention concerns a light diffuser according to the generic term of the first independent claim, as well as a method for producing the light diffuser according to the generic term of the corresponding independent claim. The light diffuser according to the invention is suitable for the diffuse deflection of light delivered to the diffuser from a light source or through a light conductor in an essentially axial direction. The light diffuser according to the invention is e.g. suitable for application in endoscopic methods, e.g. for the targeted introduction of diffuse light into tissue structures, in particular into bone tissue, and for the consistent illumination of hollow biological structures.
2. Description of Related Art
Diffuse light is applied in tissue structures e.g. in the so-called photodynamic therapy methods known in particular for the treatment of tumorigenic diseases. For this purpose a substance, which is sensitive to light and accumulates mainly in the tumorous tissue, is administered to a patient. Then the tumorous tissue is illuminated with light of a specific wavelength, which activates the photosensitive substance and triggers a chemical reaction, which in turn destroys the tumorous cells.
Activating the photosensitive substance by light initiates the destruction of the tumorous cells. It is therefore important to be able to introduce a specific dose of light adjusted to the size of the tumour in a targeted manner and as homogenously as possible into the tumorous tissue, which is usually achieved by means of a light conductor, wherein the distal end of the light conductor is designed as a diffuser. The task of the diffuser is to scatter the light, which propagates essentially axially inside the light conductor, in as many different directions as possible and as evenly as possible. The diffuser is brought to, or introduced into the tissue to be illuminated and is supplied by the light conductor with light of a given wavelength. The diffuser distributes the light introduced by the light conductor as homogenously as possible in a space whose shape is advantageously adapted to the circumstances.
Such diffusers are known to be manufactured by corresponding modification of the distal end of a light conductor and/or by placing an appropriately equipped end-piece on or at the distal end of the light conductor. Thus e.g. the sleeve placed around the light conducting fibre is removed at the distal end of the light conductor and the surface of the light conducting fibre is roughened slightly, etched or treated with suitable tools to create a light scattering surface, as it is disclosed e.g. in the publication FR-2782778. Light scattering end-pieces usually comprise a transparent material filled with particles (e.g. transparent plastics with particles of aluminium oxide or titanium oxide). In case the light scattering effect of the modified fibre surface and/or of the end piece does not suffice to deflect an adequate portion of the supplied light from the axial direction, it is also suggested that a mirror is positioned at the distal end of the light conductor or of the diffuser, reflecting non-deflected light back into the diffuser area (e.g. disclosed in U.S. Pat. No. 5,695,583, US-2002/0094161 and U.S. Pat. No. 5,431,647).
Known light diffusers, thus, essentially represent the distal end of a light conductor and for medical purposes are brought to, or introduced into the tissue to be treated with minimally invasive methods and removed after the treatment. For the treatment, the proximal end of the light conductor is attached to a light source, wherein the light source is e.g. a laser, but can also be the distal end of another light conductor.
The known diffusers described above are manufactured by relatively elaborate methods and are therefore expensive. They nevertheless have to be treated as disposable items as they are difficult to clean and sterilize and the risk of infection is clinically often considered too high for a repeated application. For photo-dynamic therapy, the diffuser has to be brought into the immediate vicinity of, or even into the tissue to be treated and it has to be retracted from this tissue after the treatment, which is connected with the danger of diseased cells, e.g. metastasizing tumorous cells, being spread.